ABSTRACT
A new stereoselective HPLC assay was developed to isolate omeprazole enantiomers from human plasma using C2 solid-phase extraction cartridges and an analogue was used as internal standard. Recoveries of the (+)-isomer were 83.4 and 89.7% at 100 and 250 ng/ml, respectively. Recoveries of the (-)-isomer were 78.4 and 82.8%, respectively. Recovery of the internal standard averaged 77.2%. Direct chiral separation of the enantiomers is achieved on a Resolvosil BSA-7 chiral column (15 cm x 4 mm I.D.) and a matching guard column. The mobile phase is a variable amount of n-propanol (0.05-1.0%) in 0.05 M ammonium phosphate buffer (pH 7.0) and the flow-rate is 1.5 ml/min. Drug absorbance is monitored at 302 nm. Standard curves are linear from 15 to 250 ng/ml for each enantiomer. The coefficients of variation for intra-day precision at each concentration over the range of the standard curve were between 0.98 and 10.87%. The coefficients of variation for inter-day precision for the analyses of omeprazole enantiomers in plasma (30 and 175 ng/ml) were less than 10% over a four month interval.
Subject(s)
Chromatography, High Pressure Liquid/methods , Omeprazole/blood , Humans , Reference Standards , Reproducibility of Results , StereoisomerismABSTRACT
A sensitive reversed-phase high-performance liquid chromatographic method with ultraviolet detection was developed for the analysis of a new angiotensin II receptor antagonist, DuP 532 (L-694,492), in human plasma and urine. The analyte and internal standard are extracted from plasma and urine at a pH between 3.3 to 3.6 by liquid-liquid extraction and analyzed on a C6 column with ultraviolet detection at 254 nm. The mobile phase is composed of acetonitrile and phosphate buffer at pH 2.5. The limits of quantification are 6 and 7.5 ng/ml for plasma and urine, respectively.
Subject(s)
Angiotensin Receptor Antagonists , Chromatography, High Pressure Liquid/methods , Imidazoles/metabolism , Tetrazoles/metabolism , Humans , Imidazoles/blood , Imidazoles/urine , Reproducibility of Results , Spectrophotometry, Ultraviolet , Tetrazoles/blood , Tetrazoles/urineABSTRACT
A sensitive method is described for the measurement of remoxipride in human plasma and urine. Remoxipride and its internal standard are extracted from plasma or urine at pH 12 with a mixture of hexane and methyl tert.-butyl ether. After washing the organic phase with base, the compounds are extracted into acid and analyzed on a C18 column with ultraviolet detection at 214 nm. The mobile phase is composed of acetonitrile and aqueous buffer (sodium perchlorate and phosphoric acid, pH 1.7). The limits of reliable quantitation for remoxipride are 12.5 and 50 ng/ml for plasma and urine, respectively. The run times are 6 min for plasma and 3 min for urine. The method has been successfully used to assay remoxipride clinical study samples. This mobile phase has also been successfully applied to the analysis of other basic drugs such as cimetidine, codeine, diltiazem and quinidine with minor modifications.
